1. Field of the Invention
The present invention relates to a substrate processing system and a substrate processing method for performing a sequence of processes for various types of substrates such as semiconductor wafers and liquid crystal display (LCD) glass substrates.
2. Description of the Related Art
In fabrication processes for semiconductor devices and LCD glass substrates (LCD substrates), fine circuit patterns are formed using a photolithography technology. In the photolithography technology, a resist is coated in a film shape on the front surface of a raw substrate such as an LCD substrate or a semiconductor wafer and then exposed with a predetermined pattern. After the exposed pattern is developed and etched., a desired circuit pattern is obtained.
Recently, as the sizes of semiconductor wafers are becoming large, in the photolithography process, wafers are successively processed. For example, in a complex processing system that performs both of a resist coating process and a developing process, wafers are extracted from a cassette one by one. The extracted wafers are processed in a processing unit one by one. The processed wafers are returned to a cassette. For example, 25 semiconductor wafers are treated as one lot. A recipe (namely, a process program) is set to each lot. The heating process conditions such as pre-bake temperature and post-bake temperature depend on the recipe that is used. Thus, wafers W of the same lot are heat-processed in the same conditions.
In such a complex processing system, one unit is required for each process. However, when only one unit performs a designated process, the process time depends on the unit that is used. In other words, one unit requires a long process time, whereas another unit does not require a long process time. Such time differences cause the throughput of the system to lower. To solve such a problem, for a process that requires a long process time, a plurality of units are used for the same process (for example, two developing units are used) so as to prevent one process from being adversely affected by another process and thereby improving the throughput of the system. Such a method is referred to as multi-units for single-process method. In addition, for example, the cooling process and the heating process should be performed a plurality of times. However, such processes can be performed by the same units with different process conditions. Thus, it is not necessary to assign each process to each unit. Consequently, when all heating processes and cooling processes are shared in each flow, they can be effectively used.
In addition, when one process is performed by a plurality of processing units, before real processes are started, the processing units should be assigned.
However, in the case of for example a heat processing unit, if the unit is used as a pre-baking unit in the processes for the first lot and then used as a pre-baking unit in the processes for the second lot, assuming that the last temperature of the baking process for the first lot is 120xc2x0 C. and that the first temperature of the baking process for the second lot is 180xc2x0 C., it takes a long time to raise the temperature with the heater of the heat processing unit. Thus, when processing units are assigned, since it takes a long time until they accomplish desired temperatures, the throughput of the system becomes low.
To prevent the throughput of the system from lowering, the baking unit used for the first lot is not assigned. Instead, an unused baking unit is selected. Thus, when an unused baking unit is pre-heated, since it is not necessary to stop the processes until the heater accomplishes a predetermined temperature, the processes can be successively performed. However, it takes a long time until an unused baking unit at the room temperature accomplishes a predetermined temperature. In addition, the power supplied to the heater increases. Thus, the power consumption increases. In addition, when an unit for the second lot is selected, there m ay be no unused baking unit for the first lot.
An object of the present invention is to provide a substrate processing system and a substrate processing method that are capable of selecting optimum processing units.
A first aspect of the present invention is a substrate processing system, comprising a processing portion having a plurality of processing units for performing a plurality of processes for a first substrate and a second substrate, a conveying portion, disposed in the processing portion, for exchanging the first substrate with the second substrate at least between the processing units, a process procedure setting portion for set ting a process procedure that includes process conditions corresponding to the first substrate and the second substrate, and a selecting portion for obtaining a process start prediction time at which the process of each of the processing unit is started for the first substrate and the second substrate and a process completion prediction time at which the process of each of the processing units is completed for the first substrate and the second substrate corresponding to the process procedure and for selecting at least one of optimum processing units that optimize the processes for each of the first substrate and the second substrate in each of said first substrate and said second substrate corresponding to the process start prediction time and the process completion prediction time, the process start prediction time and the process completion prediction time being obtained for at least two processes.
A second aspect of the present invention is a substrate processing system, comprising a loading/unloading portion for loading a cassette that contains a plurality of unprocessed substrates for one lot and for unloading a cassette that contains a plurality of processed substrates for one lot, a processing portion having a plurality of processing units for performing a plurality of processes for a substrate, a conveying portion, disposed in the processing portion, exchanging substrates with the loading/unloading portion and successively conveying the substrates to the processing units, a process procedure setting portion for setting a process procedure that includes at least process conditions for at least each of lots, and a calculation processing portion for calculating a process start prediction time at which the process of each processing unit is started for each of lots and a process completion prediction time at which the process of each processing unit is completed for each of lots and for selecting at least one of optimum processing units that optimize processes for each of lots corresponding to the process start prediction time and the process completion prediction time, the process start prediction time and the process completion prediction time being obtained for at least two processes.
In the example, the process procedure contains at least information that designates a processing unit. More preferably, the process procedure contains a process recipe such as real process times of individual processing units and process conditions thereof.
Thus, corresponding to a process procedure, a process start prediction time at which the process of each processing unit is started and a process completion prediction time at which the process of each processing unit is completed are calculated for each lot. Corresponding to the process start time and the process completion time, an optimum processing unit that optimizes the process for each lot is selected. Thus, after the process of each processing unit is completed, another process can be smoothly started with other conditions.
Preferably, there is no unused processing units for each lot. An optimum processing unit is selected from the unused processing units. Thus, from all processing units used for a particular lot, an optimum processing unit that satisfies process conditions can be selected even if any processing unit cannot accomplish a recipe for the next lot.
The calculation processing portion preferably selects optimum processing units that accomplish the process procedure in shorter time periods after the process completion prediction time for one lot until the process start prediction time for the next lot. Thus, the control amount of a processing unit until it accomplishes a process procedure (for example, the amount of power supplied to the heater of the heat processing unit) can be decreased. Consequently, the power consumption can be decreased. In addition, the process cycle time period in the regular state of the system can be shortened.
The processing units preferably include at least two heat processing units. The process procedure preferably contains a set temperature for each of the heat processing units for each lot. The calculation processing portion more preferably selects an optimum processing unit from a plurality of heat processing units corresponding to the set temperature. Thus, units that accomplish a set temperature in shorter time periods can be successively selected. Consequently, the amount of power supplied to the heating mechanism of each heat processing unit can be decreased.
The calculation processing portion preferably has a storing portion for storing a heating characteristic curve and a cooling characteristic curve for the heat processing units. The calculation processing portion preferably selects an optimum processing unit corresponding to the heating characteristic curve and the cooling characteristic curve stored in the storing portion.
The calculation processing portion has a storing portion. The calculation processing portion preferably calculates the process start prediction time and the process completion prediction time corresponding to past process procedures and completion times stored in the storing portion.
The calculation processing portion preferably calculates a start time at which each of the heat processing units starts controlling a temperature corresponding to the process completion prediction time, the process start prediction time, the heating characteristic curve, and the cooling characteristic curve. Thus, in the shortest temperature control time period, lots can be successively processed. For example, a heater is disposed in an unit. The time at which the power is supplied to the heater is calculated. Thus, the timing at which the power is supplied to the heater is obtained. Consequently, the amount of power supplied to the heater can be minimized.
The calculation processing portion calculates the process start prediction time and the process completion prediction time corresponding to a process completion prediction time for predicting a timing for processes for one lot and to a process cycle time period of each of the processing units. Thus, the process start prediction time and the process completion prediction time can be easily calculated. The process completion prediction time may be one of a first process completion prediction time after the first substrate of one lot is conveyed to a processing unit until the first substrate is returned to the loading/unloading portion, a second process completion prediction time after the first substrate of one lot is conveyed to a processing unit until all substrates of the same lot are conveyed to the processing unit, or a third process completion prediction time after the first substrate of one lot is conveyed to a processing unit until all substrates of the same lot are retuned from the processing unit to the loading/unloading portion.
The calculation processing portion preferably has a storing portion for storing an elapsed time after the cassette changeable time period until a cassette change completion time. Thus, even if the operator forgot to change a cassette and thereby the successive lot processes stopped, the temperature control start time at which the heat processing unit starts the temperature control can be compensated. Thus, in such a case, the temperature can be accurately controlled. The cassette changeable time period is a time period for which a cassette can be changed for the next lot. After the cassette changeable time period elapsed, if a cassette is changed, the successive lot processes are stopped.
A third aspect of the present invention is a substrate processing method for successively extracting unprocessed substrates, successively conveying the extracted substrates to a plurality of processing units, causing the processing units to process the conveyed substrates, and successively returning the processed substrates to a cassette, the method comprising the steps of calculating a process start prediction time at which the processes for each lot are started and a process completion prediction time at which the processes for each lot are completed for each lot corresponding to a process procedure that contains process conditions for each of at least one lot, the process start prediction time and the process completion prediction time being calculated for at least two processes, and selecting at least one of optimum processing units for each lot for optimizing processes in said individual lot corresponding to the process start prediction time and the process completion prediction time.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawings.